Stabilization of Cytosine Deaminase from Bakers’ Yeast by Immobilization

Abstract

Cytosine deaminase (EC 3.5.4.1) from bakers’ yeast, which is labile to heat, the half-life being about 30 min at 37°C, was stabilized through immobilization by various techniques. Our purpose was to prepare implantable enzyme capsules for long-term use in cancer chemotherapy [J. Biotechnol., 2, 13 (1985)]. When the enzyme was immobilized on Eupergit C, a commercial epoxy-acrylic resin, the highest yield of apparent enzymic activity was about 80% of the starting activity, and the enzymic activity decayed exponentially at 37°C over a few weeks, the half-life being about 10 days. With lower yields, other commercial adsorbents resulted in good stability; with yields of 20~67 and 21 %, and half-lives of 15 and 24 days for Formyl-Cellulofine and CNBr-activated Sepharose 4B, respectively.